Molds & Tooling
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PPO Shrinkage Directionality
Problem Phenomenon
PPO glass fiber reinforced products show obvious dimensional directionality differences, shrinkage differs between the flow direction and the perpendicular direction, and assembly fits are out of tolerance.
Cause Analysis
Glass fiber orientation causes shrinkage to exhibit directionality; shrinkage is small in the flow direction where fibers align, and large in the perpendicular direction; gate position determines the orientation pattern; wall thickness affects the degree of orientation.
Solution
①Compensate shrinkage separately by direction in mold design; ②optimize gate position for orientation distribution; ③measure shrinkage rates in both directions during mold trials; ④focus on verifying critical fit dimensions.
Key Takeaway
Directional shrinkage of PPO glass fiber parts is an inherent characteristic; directional compensation is a key point of mold design; measured data is more reliable than theoretical values.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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